OF THE SEA AND LAND. 11 



pies of this ; but none better than the plain of the 

 Ganges, respecting which all may read what I have 

 no room to quote. 



I must here also notice one consequence occurring 

 in the lower portion of a river, where art has inter- 

 fered ; from its great economical importance. 1 he 

 tendency of the stream is to wander, and it is the object of 

 embankments to restrain that, as to check inundation. 

 Hence the materials with which the water would have 

 elevated the plain, in the performance of its appointed 

 duty, become deposited in the channel; thus raising its 

 bed, and therefore rendering necessary a higher em- 

 bankment, and also a prolongation of that towards its 

 source. Thus is the river forced up above the plain, 

 and thus does the plain itself become a depressed mea- 

 dow, often difficult of drainage, and often a marsh : 

 while the gradual extension of these upwards, with a 

 comparative depression of their level, produces and 

 extends those lands which are the notorious sources of 

 disease. Such is the well-known state of the Mississipi 

 at New Orleans, and such is that of the Po ; now 

 running, in some parts, almost on the summit of a 

 dyke, so as to have led to serious reflections on the ne- 

 cessity of allowing it to break loose and find a new 

 bed. And that this also is the state of the Thames, I 

 need not say ; while the pressing result at present, is 

 the increasing depression of Westminster beneath the 

 full stream. 



The last remark respecting the shifting of rivers is 

 important, on account of some false conclusions, of the 

 usual nature, drawn from the traces which they have 

 left where they no longer flow, or from great accumu- 

 lations of alluvia in the course of a mere rill. Re- 

 specting the former, I need add no more : he who will 

 exert himself will often find the real causes of what he 

 desires to think a " diluvium," and probably a relic of 



